1. Field of the Invention
The invention relates to an electric generator, more particularly to an electric generator for use with a vehicle wheel.
2. Description of the Related Art
FIG. 1 illustrates a conventional electric generator 2 for use with a bicycle 1. The conventional electric generator 2 is mounted on a wheel axle 12 and provides electric power to a lamp 13 mounted on the bicycle 1.
Referring to FIG. 2, the conventional electric generator 2 is shown to include a housing 21, three stator coils 22, and three magnet rings 23. The housing 21 is secured to a wheel hub 14 on the wheel axle 12 such that the housing 21 is capable of rotating about the wheel axle 12 when a bicycle wheel 11 (see FIG. 1) rotates. The stator coils 22, which are connected in series, are disposed in the housing 21 and are mounted on the wheel axle 12. The magnet rings 23 are disposed in the housing 21 around the stator coils 22, and are mounted on an inner surface of the housing 21.
As such, rotation of the magnet rings 23 with the housing 21 when the bicycle wheel 11 rotates results in an induced electrical current in the stator coils 22 that is provided to the lamp 12 via a cable 24.
The following are some of the drawbacks of the conventional electric generator 2:
1. The bicycle wheel 11 must be detached when it is desired to install the electric generator 2.
2. Variations in speed of rotation of the bicycle wheel 11 results in an unstable induced electrical current such that the service life of the lamp 13 is adversely affected.
Therefore, the object of the present invention is to provide an electric generator for use with a vehicle wheel that can eliminate the aforesaid drawbacks of the prior art.
According to the present invention, there is provided an electric generator adapted for use with a vehicle wheel. The electric generator comprises:
a housing adapted to be mounted on the vehicle wheel and having a base wall and a surrounding wall that extends from a periphery of the base wall and that cooperates with the base wall to confine a receiving space, the surrounding wall being formed with inlet and outlet vent holes that are in spatial communication with the receiving space;
an air impeller disposed in the receiving space and having a spindle that extends in an,axial direction transverse to the base wall and that is coupled rotatably to the base wall, the air impeller being formed with a plurality of radial impeller blades such that flow of air into the receiving space through the inlet vent hole and out of the receiving space through the outlet vent hole when the vehicle wheel rotates results in rotation of the air impeller in the receiving space;
a stator coil mounted securely in the receiving space; and
a magnet ring disposed in the receiving space around the stator coil and coupled co-rotatably to the air impeller such that rotation of the magnet ring with the air impeller results in an induced electrical current in the stator coil.